One of important functions of a welding robot is weaving a weld between members being welded thereby. As is well known in the art, such weaving is a welding method of oscillating a welding torch substantially perpendicularly to a weld line to move the same along the weld line. In a conventional control method for making the welding robot perform such weaving, generally the oscillation width in the perpendicular direction, i.e., the weaving width amplitude is previously set in a computer as a constant value, to oscillate the forward end of the torch of the welding robot in the constant weaving amplitude and thereby to perform welding.
However, in the workpiece to be welded (hereinafter referred to as "welded member", and when two members are to be welded to each other, as "first" and "second" welded members respectively), the butting space and bevel width between the first and second welded members (generically referred to as an "interspace" between the welded members) are frequently not uniform in the weld line direction. This is due to variations and integrated errors in cutting accuracy, bending accuracy and assembling accuracy caused by bending and distortion of materials. When such welded members are joined by a weld woven by a welding robot through application of the conventional control method, the welding is performed in the constant weaving amplitude regardless of the nonuniformity of the interspace therebetween, whereby under-and-overwelding is caused depending on positions, to very seriously lower the weld quality.
Therefore, manual welding has been generally required to weave welded members having a ununiform interspace between them.